U.S. patent number 9,399,820 [Application Number 14/368,589] was granted by the patent office on 2016-07-26 for electroless nickel plating bath.
This patent grant is currently assigned to Atotech Deutschland GmbH. The grantee listed for this patent is Atotech Deutschland GmbH. Invention is credited to Brigitte Dyrbusch, Carl Christian Fels.
United States Patent |
9,399,820 |
Fels , et al. |
July 26, 2016 |
Electroless nickel plating bath
Abstract
The present invention concerns an electroless nickel plating
bath suitable for application in plating on plastic processes. The
plating bath is free of hazardous substances such as lead ions and
ammonia and allows deposition of nickel phosphorous alloys on
plastic substrates at plating temperatures not higher than
55.degree. C. Furthermore, the deposition of copper from an
immersion type copper plating bath onto the nickel phosphorous
coatings require no activation step which results in less process
steps and less waste water production.
Inventors: |
Fels; Carl Christian (Berlin,
DE), Dyrbusch; Brigitte (Berlin, DE) |
Applicant: |
Name |
City |
State |
Country |
Type |
Atotech Deutschland GmbH |
Berlin |
N/A |
DE |
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|
Assignee: |
Atotech Deutschland GmbH
(Berlin, DE)
|
Family
ID: |
47624100 |
Appl.
No.: |
14/368,589 |
Filed: |
January 31, 2013 |
PCT
Filed: |
January 31, 2013 |
PCT No.: |
PCT/EP2013/051889 |
371(c)(1),(2),(4) Date: |
June 25, 2014 |
PCT
Pub. No.: |
WO2013/113810 |
PCT
Pub. Date: |
August 08, 2013 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20150159274 A1 |
Jun 11, 2015 |
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Foreign Application Priority Data
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Feb 1, 2012 [EP] |
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12153540 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23C
18/30 (20130101); C23C 18/54 (20130101); C23C
18/2086 (20130101); C23C 18/1651 (20130101); C23C
18/285 (20130101); C23C 18/1633 (20130101); C23C
18/24 (20130101); C23C 18/1653 (20130101); C23C
18/36 (20130101); C23C 18/165 (20130101) |
Current International
Class: |
C23C
18/18 (20060101); C23C 18/16 (20060101); C23C
18/28 (20060101); C23C 18/30 (20060101); C23C
18/36 (20060101); C23C 18/54 (20060101); C23C
18/20 (20060101); C23C 18/24 (20060101) |
Field of
Search: |
;205/183
;427/301,305,438,443.1 ;174/254 ;106/1.22,1.27 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2001342453 |
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Dec 2001 |
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JP |
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200582883 |
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Mar 2005 |
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JP |
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WO 2006102182 |
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Sep 2006 |
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WO |
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Other References
Kolodynska, "Iminodisuccinic acid as a new complexing agent for
removal of heavy metal ions from industrial effluents" Chemical
Engineering Journal, vol. 152, Issue 1, Oct. 1, 2009, pp. 277-288.
cited by examiner .
English translation of JP2001342453. cited by examiner .
Database WPI Week 201234, Thomson Scientific, London, GB; AN
2012-A51526; XP002678882,& CN 102 286 735 A (Byd Co Ltd) Dec.
21, 2011. cited by applicant .
PCT/EP2013/051889; PCT International Search Report and Written
Opinion of the International Searching Authority dated May 8, 2014.
cited by applicant .
PCT/EP2013/051889; PCT International Preliminary Report on
Patentability mailed Dec. 11, 2014. cited by applicant.
|
Primary Examiner: Klemanski; Helene
Attorney, Agent or Firm: Renner, Otto, Boisselle &
Sklar, LLP
Claims
The invention claimed is:
1. An ammonia- and lead-free electroless nickel plating bath for
deposition of nickel phosphorus alloys having a phosphorus content
of 6 to 9 wt.-% comprising i. a source of nickel ions, at a
concentration of 2.5 g/l to 4 g/l, ii. a source of hypophosphite
ions, at a concentration of 20 g/l to 27 g/l, iii. a complexant
mixture comprising a) at least one first complexant at a
concentration of from 1 g/l to 50 g/l selected from the group
consisting of hydroxy carboxylic acids, dihydroxy carboxylic acids
and salts thereof and b) at least one second complexant at a
concentration of from 0.2 g/l to 10 g/l selected from the group
consisting of iminosuccinic acid, iminodisuccinic acid, salts and
derivatives thereof, iv. a stabilizer mixture comprising a) bismuth
ions, at a concentration of 0.5 mg/l to 30 mg/l and b) at least one
compound selected from the group consisting of mercapto benzoic
acids, mercapto carboxylic acids and mercapto sulfonic acids and
salts thereof, at a concentration of 0.1 mg/l to 100 mg/l, wherein
the bath has a pH in the range from 6.5 to 11.5.
2. An electroless nickel plating bath according to claim 1 wherein
the at least one first complexant is selected from the group
consisting of hydroxymalonic acid, glycolic acid, lactic acid,
citric acid, mandelic acid, tartaric acid, malic acid, paratartaric
acid, succinic acid, aspartic acid and salts thereof.
3. An electroless nickel plating bath according to claim 1 wherein
the concentration of the at least one first complexant ranges from
10 g/l to 20 g/l.
4. An electroless nickel plating bath according to claim 1 wherein
the concentration of the at least one second complexant ranges from
0.8 g/l to 5 g/l.
5. An electroless nickel plating bath according to claim 1 wherein
the concentration of bismuth ions ranges from 1 mg/l to 30
mg/l.
6. An electroless nickel plating bath according to claim 1 wherein
the mercapto benzoic acid derivative is selected from the group
consisting of 2-mercapto benzoic acid, 3-mercapto benzoic acid,
4-mercapto benzoic acid, salts thereof and mixtures thereof.
7. An electroless nickel plating bath according to claim 1 wherein
the mercapto carboxylic acid is selected from the group consisting
of 3-mercaptopropionic acid, 3-mercapto-2-methylpropionic acid,
2-mercaptopropanoic acid, mercapto acetic acid, 4-mercaptobutyric
acid and 3-mercaptoisobutyric acid.
8. An electroless nickel plating bath according to claim 1 wherein
the mercapto sulfonic acid is selected from the group consisting of
2-mercapto-1-ethane sulfonic acid, 3-mercapto-1-propane sulfonic
acid, and 4-mercapto-1-butane sulfonic acid.
9. An electroless nickel plating bath according to claim 1 wherein
the concentration of the mercapto benzoic acids, mercapto
carboxylic acids and mercapto sulfonic acids and salts thereof
ranges from 0.5 mg/l to 30 mg/l.
10. A method for metal plating of non-conductive substrates, which
comprises the following steps: i. providing a conductive seed layer
onto the non-conductive substrate; ii. applying a nickel
phosphorous coating to said non-conductive substrate by bringing it
into contact with a plating bath composition according to claim 1
at a temperature in the range of 25 to 35.degree. for a time
ranging from 4 to 120 min; iii. optionally, rinsing the such plated
substrate with water; and iv. applying a copper coating onto the
nickel phosphorous coating by bringing the plastic substrate into
contact with an immersion copper plating bath comprising copper
ions, wherein a nickel phosphorus alloy having a phosphorus content
of 6 to 9 wt.-% is deposited on the substrate.
11. A method according to claim 10, wherein the plating temperature
ranges between 27-32.degree..
12. A method according to claim 10, wherein the non-conductive
substrate is a plastic substrate made of ABS or ABS/PC blend.
13. A method according to claim 10, further comprising v. applying
at least one electrolytically deposited metal layer onto the
immersion copper layer deposited in step iv., wherein the at least
one electrolytically deposited layer is selected from copper,
nickel, chromium or its alloys.
14. A method according to claim 11, wherein the non-conductive
substrate is a plastic substrate made of ABS or ABS/PC blend.
15. A method according to claim 11, further comprising v. applying
at least one electrolytically deposited metal layer onto the
immersion copper layer deposited in step iv., wherein the at least
one electrolytically deposited layer is selected from copper,
nickel, chromium or its alloys.
16. A method according to claim 12, further comprising v. applying
at least one electrolytically deposited metal layer onto the
immersion copper layer deposited in step iv., wherein the at least
one electrolytically deposited layer is selected from copper,
nickel, chromium or its alloys.
Description
The present application is a U.S. National Stage Application based
on and claiming benefit and priority under 35 U.S.C. .sctn.371 of
International Application No. PCT/EP2013/051889, filed 31 Jan.
2013, which in turn claims benefit of and priority to European
Application No. 12153540.5, filed 1 Feb. 2012, the entirety of each
of which is hereby incorporated herein by reference.
FIELD OF THE INVENTION
The invention relates to an electroless nickel plating bath for a
low-temperature deposition of nickel phosphorus alloys having a
phosphorus content of 4 to 11 wt.-%. The derived nickel phosphorus
deposits can be directly coated with copper from an immersion
copper plating bath during a plating on plastic process.
BACKGROUND OF THE INVENTION
Plating on plastic processes for decorative and electromagnetic
impedance shielding purposes are widely used in the industry. Said
processes are applied to various plastic parts such as shower
heads, mobile phone covers and radiator grills. One main process
route involves an electroless plating step after pre-treatment and
activation of the plastic substrate to be coated. The electroless
plating methods applied are usually electroless deposition of
copper or nickel. The metal or metal alloy layer deposited onto the
activated plastic substrate serve as a full area conductive surface
for further metal layers deposited later by electroplating methods.
The main plastic materials used for said purpose are ABS
(acrylonitrile-butadiene-styrene copolymer), ABS/PC blends and PA.
The main electroplating processes applied after electroless
deposition of copper or nickel are plating of copper, nickel and
finally chromium. Such methods are well known in the art and for
example described in EP 0 616 053 B1.
In case a nickel alloy is deposited by an electroless plating
method the requirements for the electroless nickel plating process
and the nickel plating bath used are manifold.
Electroless nickel plating baths capable for deposition of nickel
phosphorus alloys having a phosphorus content in the range of 4 to
11 wt.-% are known in the art.
An electroless nickel plating bath useful for deposition of nickel
phosphorous alloys onto conducting SnO.sub.2 surfaces is disclosed
in US 2002/0187266 A1. Said electroless nickel plating bath may
contain thiosalicylic acid as a stabilizing agent. However,
disclosed plating temperatures are as high as 70.degree. C. and the
plating bath requires hazardous substances such as lead ions.
An electroless nickel plating bath comprising sulphide ions
together with a sulphide ion controller is disclosed in U.S. Pat.
No. 2,762,723. Compounds suitable as sulphide ion controller are
selected from inorganic sulphides, other thio compounds, bismuth
and lead ions.
SUMMARY OF THE INVENTION
Thus, it is an object of the present invention to provide an
electroless nickel plating bath for plating on plastic process
which is capable to deposit nickel phosphorous alloys having a
phosphorus content in the range of 4 to 11 wt.-%, preferably 6 to 9
wt. %, to deposit said alloys at a plating bath temperature of not
higher than 55.degree. C., preferably below 40.degree. C. which
saves energy and which does not contain hazardous components such
as lead and ammonia. Furthermore it is an object of the present
invention to provide an electroless nickel plating bath which
allows deposition of nickel phosphorus coatings which can be coated
in a successive process step with copper from an immersion copper
plating bath without activation of the nickel phosphorus coating by
immersing the substrate in e.g., sulphuric acid prior to copper
deposition. This leads to a reduced number of process steps and
less waste water production.
This object is achieved with an lead- and ammonium-free electroless
nickel plating bath according to claim 1 comprising a nickel salt,
a hypophosphite compound as reduction agent, a complexing agent
mixture, and a stabilizer component mixture.
By applying the plating mechanism according to the present
invention using a plating bath described in more detail below
nickel phosphorous deposits can be obtained which are low in
phosphorous and suited to be directly plated by immersion
copper.
Without being bound to it, it is believed that the direct immersion
plating on nickel phosphorous deposits obtained by a method of the
present invention is possible because of lower phosphorous as well
as bismuth content of the nickel deposit, both of which negatively
effect the copper deposition.
DETAILED DESCRIPTION OF THE INVENTION
It has been surprisingly found by the inventors that nickel
phosphorus coatings on an activated plastic substrate can be
deposited from an ammonia- and lead-free electroless nickel plating
bath for deposition of nickel phosphorus alloys having a phosphorus
content of 4 to 11 wt.-% at low temperatures, which are suited for
direct deposition of immersion copper, the plating bath
comprising
1. i. a source of nickel ions ii. a source of hypophosphite ions,
iii. a complexant mixture comprising a) at least one first
complexant selected from the group consisting of hydroxy carboxylic
acids, dihydroxy carboxylic acids and salts thereof and b) at least
one second complexant selected from the group consisting of
iminosuccinic acid, iminodisuccinic acid, salts and derivatives
thereof, iv. a stabilizer mixture comprising a) bismuth ions, and
b) at least one compound selected from the group consisting of
mercapto benzoic acids, mercapto carboxylic acids and mercapto
sulfonic acids and salts thereof.
The advantages of the inventive electroless nickel plating bath are
a) ammonia and lead are not required in the plating bath and b) the
activation of a nickel phosphorus layer prior to copper deposition
from an immersion copper plating bath is not required.
The inventive electroless nickel plating bath contains nickel ions
in a concentration of 0.5 g/l to 5 g/l, more preferred 2.5 g/l to 4
g/l. The source of nickel ions is selected from water soluble
nickel salts. Preferred sources of nickel salts are selected from
the group comprising nickel chloride, nickel sulphate, nickel
methanesulfonate and nickel carbonate.
The inventive electroless nickel plating bath further contains a
reducing agent which is selected from hypophosphite compounds such
as sodium hypophosphite and potassium hypophosphite. The
concentration of hypophosphite ions in the plating bath preferably
ranges from 10 g/l to 35 g/l, more preferably from 20 g/l to 27
g/l.
The inventive electroless nickel plating bath further contains a
mixture of complexants which is constituted of at least one first
complexing agent selected from the group consisting of hydroxy
carboxylic acids, dihydroxy carboxylic acids and salts thereof.
The at least one second complexing agent is selected from the group
consisting of iminosuccinic acid, iminodisuccinic acid, derivatives
thereof and salts thereof.
The at least one first complexing agent is preferably selected from
the group consisting of hydroxymalonic acid, glycolic acid, lactic
acid, citric acid, mandelic acid, tartaric acid, malic acid,
paratartaric acid, succinic acid, aspartic acid and salts thereof.
Cations in salts of the at least one first complexing agent are
selected from lithium, sodium and potassium. The most preferred
first complexing agents are selected from the group consisting of
succinic acid, glycinic acid and glycolic acid.
The concentration of the at least one first complexing agent ranges
from 1 g/l to 50 g/l, more preferably from 10 g/l to 20 g/l.
The at least one second complexant which is selected from
iminosuccinic acid, diiminosuccinic acid, derivatives thereof or
salts thereof is selected from the group consisting of
iminosuccinic acid, iminodisuccinic acid, derivatives thereof and
salts thereof. Cations in salts of iminosuccinic acid derivatives
are selected from lithium, sodium and potassium.
The concentration of the at least one second complexing agent
ranges from 0.2 g/l to 10 g/l, more preferably from 0.8 g/l to 5
g/l.
The inventive electroless nickel plating bath composition further
contains a stabilizer mixture consisting of two components:
a bismuth salt,
mercapto benzoic acids, mercapto carboxylic acids and mercapto
sulfonic acids and salts thereof.
The bismuth salt added to the electroless nickel plating bath is a
water soluble bismuth salt selected from the group consisting of
bismuth nitrate, bismuth tartrate, bismuth sulphate, bismuth oxide
and bismuth carbonate. The concentration of bismuth ions in the
electroless nickel plating bath ranges from 0.5 mg/l to 100 mg/l,
preferably from 0.5 mg/l to 30 mg/l, more preferably from 1 mg/l to
30 mg/l.
The mercapto benzoic acid, derivative or salt thereof are selected
from the group consisting of 2-mercapto benzoic acid, 3-mercapto
benzoic acid, 4-mercapto benzoic acid, salts thereof and mixtures
thereof. Preferably the salts of the mercapto benzoic acid or
derivative thereof are selected from the group consisting of
lithium, sodium and potassium salts and mixtures of the foregoing.
The concentration of the at least one mercapto benzoic acid or salt
thereof ranges from 0.1 mg/l to 100 mg/l, more preferably 0.5 mg/l
to 30 mg/l.
The mercapto carboxylic acid is selected from the group consisting
of 3-mercaptopropionic acid, 3-mercapto-2-methylpropionic acid,
2-mercaptopropanoic acid, mercapto acetic acid, 4-mercaptobutyric
acid, 3-mercaptoisobutyric acid. Preferably the mercapto carboxylic
acid is not mercapto acetic acid. More preferably the mercapto
carboxylic acid is selected from the group consisting of
3-mercaptopropionic acid, 3-mercapto-2-methylpropionic acid,
2-mercaptopropanoic acid, 4-mercaptobutyric acid,
3-mercaptoisobutyric acid.
The mercapto sulfonic acid is selected from the group consisting of
2-mercapto-1-ethane sulfonic acid, 3-mercapto-1-propane sulfonic
acid, 4-mercapto-1-butane sulfonic acid.
The concentration of the at least one mercapto carboxyl acid or
mercapto sulfonic acid or salt thereof ranges from 0.1 mg/l to 100
mg/l, more preferably 0.5 mg/l to 30 mg/l.
The pH value of the inventive nickel phosphorous plating bath
ranges from 6.5 to 11.5, preferably 6.5 to 9.0.
The nickel phosphorous plating bath is held at a temperature in the
range of 20 to 55.degree. C., preferably in the range of 25 to
35.degree. C., more preferably in the range of 27 to 32.degree. C.
during plating.
The plating time ranges from 4 to 120 min.
During the deposition of the nickel alloy, mild agitation of the
plating bath generally is employed; its agitation may be a mild air
agitation, mechanical agitation, bath circulation by pumping,
rotation of a barrel plating, etc. The plating solution may also be
subjected to a periodic or continuous filtration treatment to
reduce the level of contaminants therein. Replenishment of the
constituents of the bath may also be performed, in some
embodiments, on a periodic or continuous basis to maintain the
concentration of constituents, and in particular, the concentration
of nickel ions and hypophosphite ions, as well as the pH level
within the desired limits.
The nickel phosphorous plating bath can preferably be employed in
the plating of non-conductive plastic substrates, which generally
comprises the following steps: a) provide a conductive seed layer
onto the plastic substrate b) apply a nickel phosphorous coating to
said plastic substrate by bringing it into contact with above
mentioned plating bath composition, c) optionally, rinse the such
plated plastic substrate with water and d) apply a copper coating
onto the nickel phosphorous coating by bringing the plastic
substrate into contact with an immersion copper plating bath
comprising copper ions.
No additional activation step of the nickel phosphorous coating is
required before the copper immersion plating in step d).
The non-conductive substrates can be activated according to step a)
by various methods which are described, for example, in Handbuch
der Leiterplattentechnik, Vol. 4, 2003, pages 292 to 300. These
processes involve the formation of a conductive layer comprising
carbon particles, Pd colloids or conductive polymers. Some of these
processes are described in the patent literature and examples are
given below:
European patent EP 0 616 053 describes a process for applying a
metal coating to a non-conductive substrate (without an electroless
coating) comprising:
a. contacting said substrate with an activator comprising a noble
metal/Group IVA metal sol to obtain a treated substrate;
b. contacting said treated substrate with a self accelerating and
replenishing immersion metal composition having a pH above 11 to pH
13 comprising a solution of; (i) a Cu(II), Ag, Au or Ni soluble
metal salt or mixtures thereof, (ii) a Group IA metal hydroxide,
(iii) a complexing agent comprising an organic material having a
cumulative formation constant log K of from 0.73 to 21.95 for an
ion of the metal of said metal salt.
U.S. Pat. No. 5,503,877 describes the metallisation of
non-conductive substrates involving the use of complex compounds
for the generation of metal seeds on a non-metallic substrate.
These metal seeds provide for sufficient conductivity for
subsequent electroplating. This process is known in the art as the
so-called "Neoganth" process.
Preferably, the following process sequence is applied: a) provide a
conductive seed layer onto the plastic substrate by first etching
the substrate, e.g. an ABS plastic substrate, in an aqueous
solution containing 100-400 g/l CrO.sub.3 and 100-500 g/l sulphuric
acid at elevated temperatures between 50 to 80.degree. C., b) apply
a nickel phosphorous coating to said plastic substrate by bringing
it into contact with above mentioned plating bath composition, c)
optionally, rinse the such plated plastic substrate with water and
d) apply a copper coating onto the nickel phosphorous coating by
bringing the plastic substrate into contact with an immersion
copper plating bath comprising copper ions and sulphuric acid.
Generally, immersion copper plating baths contain a source of
copper ions, e.g. copper sulphate. The copper ion concentration can
vary depending on the plating process. It can for example range
between 0.5-1.0 g/l. Generally, it is slightly acidic and contains
an inorganic acid like sulphuric acid. Additionally additives like
surfactants can be added if required. Such additives are known in
the art.
Thereafter, the such coated substrates can be further metallised by
electrochemical methods with copper, chromium, nickel etc. known in
the art.
EXAMPLES
The invention will now be illustrated by reference to the following
non-limiting examples.
Pre-treatment of the ABS substrate material prior to deposition of
a nickel phosphorus material applied for all examples:
The ABS substrates were first etched in an aqueous solution
containing 360 g/l CrO.sub.3 and 360 g/l conc. sulphuric acid
heated to 65.degree. C. for 6 min. Next the substrates were rinsed
with water, dipped into an aqueous solution of sodium hydrogen
sulfite and again rinsed with water. Next, the ABS substrates were
dipped into an aqueous solution of 300 ml/l conc. hydrochloric
acid, activated for 1 min in an aqueous solution consisting of 300
ml/l conc. hydrochloric acid, 250 mg/l palladium chloride and 17
g/l tin(II)chloride and rinsed with water again.
After deposition of the nickel phosphorus alloy coating from
electroless nickel plating baths the ABS substrates of Examples 1
to 4 were rinsed with water and then subjected without any further
activation for 2 min to an immersion copper plating bath comprising
0.7 g/l of copper ions and 1.7 g/l conc. sulphuric acid held at
35.degree. C.
The phosphorus content of the nickel phosphorus alloy deposits was
measured with AAS (atomic absorption spectrometry) after
dissolution of the deposits.
The contact resistivity of the derived copper coating was measured
with a standard multimeter and 1 cm distance between the contact
tips. The lower the contact resistivity of a sample, the better the
coverage of the nickel phosphorus layer coated with copper.
Example 1
According to Invention
A nickel phosphorous alloy was deposited from an aqueous
electroless nickel plating bath containing 3.5 g/l nickel ions, 25
g/l hypophosphite ions (corresponding to 11.9 g/l of phosphorous),
5 g/l of citric acid and 2.5 g/l iminodiscuccinic acid as
complexant mixture and 2.7 mg/l bismuth ions and 12.8 mg/l
2-mercapto benzoic acid as stabilizer mixture.
The operating temperature of the electroless nickel plating bath
was held at 35.degree. C. and the ABS coupons were dipped into the
plating baths for 10 min.
A nickel phosphorous alloy deposit having a phosphorous content of
7.9 wt.-% was obtained.
Next the as coated substrate was rinsed with water and then dipped
without any activation directly for 2 min in an immersion copper
plating bath comprising 0.7 g/l of copper ions and 1.7 g/l conc.
sulphuric acid held at 35.degree. C. The whole nickel phosphorous
alloy layer was coated with a layer of copper.
The contact resistance of the nickel phosphorous alloy and then
copper plated ABS coupons was in the range of 0.1.OMEGA. to 1.6
.OMEGA./cm, which corresponds to a high conductivity which is
suitable for subsequent electroplating.
Example 2
According to Invention
Example 1 was repeated using an_electroless nickel plating bath
containing the same compounds except that 2-mercapto benzoic acid
as stabilizer was replaced by 15 mg/l 3-mercaptopropionic acid.
A nickel phosphorous alloy deposit having a phosphorous content of
7.6 wt.-% was obtained.
Next the as coated substrate was rinsed with water and then dipped
without any activation directly for 2 min in an immersion copper
plating bath comprising 0.7 g/l of copper ions and 1.7 g/l conc.
sulphuric acid held at 35.degree. C. The whole nickel phosphorous
alloy layer was coated with a layer of copper.
The contact resistance of the nickel phosphorous alloy and then
copper plated ABS coupons was in the range of 0.2.OMEGA. to 1.4
.OMEGA./cm, which corresponds to a high conductivity which is
suitable for subsequent electroplating.
Example 3
Comparative
Example 1 was repeated using an_electroless nickel plating bath
containing the same compounds except that 2-mercapto benzoic acid
was omitted.
A nickel phosphorous alloy deposit having a phosphorous content of
11.2 wt. % was obtained.
No immersion plating of copper was possible when treating the
deposited nickel phosphorous alloy with a copper immersion plating
solution described above.
The contact resistance of the nickel phosphorous alloy was in the
range of 40.OMEGA. to 60 .OMEGA./cm.
Example 4
Comparative
Example 1 was repeated using an_electroless nickel plating bath
containing the same compounds except that iminodisuccinic acid was
omitted.
A nickel phosphorous alloy deposit having a phosphorous content of
11.2 wt. % was obtained.
No immersion plating of copper was possible when treating the
deposited nickel phosphorous alloy with a copper immersion plating
solution described above.
The contact resistance of the nickel phosphorous alloy was in the
range of 50.OMEGA. to 70 .OMEGA./cm.
Example 5
According to Invention
A nickel phosphorous alloy was deposited from an aqueous
electroless nickel plating bath containing 3.5 g/l nickel ions, 25
g/l hypophosphite ions (corresponding to 11.9 g/l of phosphorous),
5 g/l of citric acid and 2.5 g/l iminodiscuccinic acid as
complexant mixture and 1 mg/l bismuth ions and 2 mg/l 2-mercapto
benzoic acid as stabilizer mixture. The pH value of the electroless
nickel plating bath was 8.0.
The operating temperature of the electroless nickel plating bath
was held at 35.degree. C. and the ABS coupons were dipped into the
plating bath for 10 min.
A nickel phosphorous alloy deposit having a phosphorous content of
7.23 wt.-% and a bismuth content of 0.19 wt.-% was obtained. The
deposition rate was 1.53 .mu.m/h.
Example 6
According to Invention
Example 5 was repeated using an electroless nickel plating bath
containing the same compounds except that 2-mercapto benzoic acid
as stabilizer was replaced by 5 mg/l mercapto acetic acid.
A nickel phosphorous alloy deposit having a phosphorous content of
8.5 wt.-% and a bismuth content of 0.13 wt.-% was obtained. The
deposition rate was 1.40 .mu.m/h.
Example 7
Comparative
Example 5 was repeated using an electroless nickel plating bath
containing the same compounds except that iminodisuccinic acid in
the complexant mixture was replaced by 2.5 g/l succinic acid.
A nickel phosphorous alloy deposit having a phosphorous content of
11.4 wt.-% and a bismuth content of 0.22 wt.-% was obtained. The
deposition rate was 1.43 .mu.m/h.
Example 8
Comparative
Example 5 was repeated using an electroless nickel plating bath
containing the same compounds except that 2-mercapto benzoic acid
as stabilizer was replaced by 2 mg/l thiodiglycolic acid.
A nickel phosphorous alloy deposit having a phosphorous content of
12.4 wt.-% and a bismuth content of 0.22 wt.-% was obtained. The
deposition rate was 1.28 .mu.m/h.
Example 9
According to Invention
A nickel phosphorous alloy was deposited from an aqueous
electroless nickel plating bath containing 3.5 g/l nickel ions, 25
g/l hypophosphite ions (corresponding to 11.9 g/l of phosphorous),
5 g/l of citric acid and 2.5 g/l iminodiscuccinic acid as
complexant mixture and 4 mg/l bismuth ions and 5 mg/l 2-mercapto
benzoic acid as stabilizer mixture. The pH value of the electroless
nickel plating bath was 8.6.
The operating temperature of the electroless nickel plating bath
was held at 35.degree. C. and the ABS coupons were dipped into the
plating bath for 10 min.
A nickel phosphorous alloy deposit having a phosphorous content of
8.9 wt.-% was obtained.
Example 10
According to Invention
Example 9 was repeated using an electroless nickel plating bath
containing the same compounds except that 2-mercapto benzoic acid
as stabilizer was replaced by 5 mg/l 3-mercapto-1-propane sulfonic
acid.
A nickel phosphorous alloy deposit having a phosphorous content of
8.6 wt.-% was obtained.
* * * * *